ramps1.4 24v PSU questions

I want to use a 24v heatbed on 24v psu and have 12v to everything else. I have stuff on hand already which is 24v 20A PSU , 12v 30A PSU , 24v SSR and a 24v - 12v stepdown convertor (10A) .I already have a 200W 24v kapton heater . All my other printer parts are 12v

I am thinking of using the 24v PSU with the heatbed off the SSR and the 24vPSU also goes to the 24to12v convertor which goes into the 5A and 11A input on the ramps. So only 12v at the ramps. Will this work? Since the ramps is only getting 12v can still keep the fuses,diodes etc? not need to change anything.

The other option is running the 24vPSU to SSR which powers the heatbed and use the 12v30A PSU to the ramps . Two PSU's .

What do you guys think? BTW these are the LED type power supplys not a ATX cpu PS .

With optically isolated solid-state relay you may use two independent PSU for heatbed and ramps.

This is the relay i have .
[www.ebay.com]

PSU's 12v and a 24v
[www.ebay.com]

24v to 12 convertor
[www.ebay.com]

So your saying dual PS's would be better then one 24vPS and stepdown convertor ? I wouldnt need to worry about changing fuses,capacitors,diodes on the ramps with either of these options right? Btw i have the ramps1.4 white pcb that has all 35v caps.

Not definitely better, but possible with this SSR.

Scheme with convertor possible too.

Changing ramps's components is not needed in any case.

I'm using a laptop 12v psu for everything except the heatbed. I connected the bed to a 24v psu and an automotive mechanical relay with a built in fuse (ebay) which is switched by the standard heatbed mosfet output. Disable pid, use bang bang for the bed and you're away. Very simple, very effective bed heats in about 3 minutes.

I'm not sure heat beds really need pid control anyway.

Been thinking about an old xbox psu there's a simple hack to get it to power on and it has a 5v rail 1A and 12v rail 12A.

Edited 3 time(s). Last edit at 04/15/2016 05:42PM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

I dont mind running it in BangBang mode but with the Solid State relay i have should be capable of PID control still ,correct ? The relay i have posted above says "Output 24V-380V 25A SSR-25 DA Solid State Relay For PID Temperature Controller"

Your best option is to ditch the poor Arduino/RAMPS electronics and use modern 24V-capable electronics, along with a 24V hot end heater cartridge and fans. But if you want to keep the RAMPS, you can feed 24V to the bed heater power input, and 12V to the rest. However, the 11A polyfuse on the RAMPS is only rated at 16V so it may catch fire if you get a short in the bed circuit. You can replace it by a 10A auto fuse.

Neither of these options needs an SSR if the 24V heater power is 240W or less. Whatever you do, don't try to use a cheap SSR40DD or similar purchased from eBay, because those are totally unsuitable for switching heated bed current owing to their high voltage drop.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Well im not going to ditch my ramps and other components . I am building this printer as a low cost printer with spare parts from my other printers so that would be crazy to go buy new parts for it. Right now i have all the parts i need and it has cost me under 50bucks. Only things i needed to buy was leadscrews and some couple smooth rods .

So you are saying i cant use the SSR i have ? I did just notice i may have the wrong relay anyway . Mine say 24-380VAC on the coil. I thought it was VDC . So without the relay all i need to change is the 11A Polyfuse. ?

I think you will find that the 24-380V AC rating on your SSR refers to the load side, not the control side.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

So i cant use the relay being AC on the load side. If i bought the DC version SSR? It shouldnt be a problem in bangbang mode right? I see a lot of people using this brand SSR.

Or i can change just the fuse on the ramps and connect the 24v to the 11A side and 12v to the 5A side ?

Edited 1 time(s). Last edit at 04/16/2016 01:25AM by Wadzofquadz.

Check that your bed heater has a resistance of at least 2.4 ohms, and if so then I suggest you just change the fuse on the RAMPS. The 11A side can take 24V, the 5A side only 12V on most boards. If you want more advice then I suggest you post in the RAMPS forum

Edited 1 time(s). Last edit at 04/16/2016 01:39AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Its 200W 24v 2.88ohm which i believe comes out to around 8A
[www.ultibots.com]

I did just order a Crydom D1D12 SSR in case i want to use it. Its up to 100vdc on the output and 3-32vdc on the input.

For now im gonna go with two psus . 24v to ramps 11A side with 15A car fuse inline (11A fuse removed) and 12v into the 5A side. This is all i should need to do correct?

Edited 2 time(s). Last edit at 04/16/2016 02:14AM by Wadzofquadz.